Signal modulating circuit with a cathode coupled phantastron and comparator



June 1, 1965 D. A. STARR, JR 3, 87,2 4

SIGNAL MODULATING CIRCUIT WITH A CATHODE COUPLED v PHANTASTRON AND COMPARATOR Filed Feb. 25, 1960 3| I Megohm IOOK 27 25 24 35 VOLTAGE '1 L COINCIDENCE T CIRCUIT V NEGATIVE 7| 47K PULSE GENERATOR l 23 Reference 73 S|gnol I5OV.

JNVENTOR.

DAVID A. STARR, JR. BY

ATTORNEY HEATER m United States Patent l ensues SEGNALL MGDULAM G CTRCUZT WKTH A CATHSDE CGUPLED PHANTASTRGN AND CQMLPARATGR David A. Starr, 5'12, Pauli, Pa, assignor to Burroughs (Iorporatien, Eetreit, Mich, a corporation of Michigan Filed Feb. 25, 1959, Ser. No. 10,)67 6 Ellaims. (Cl. 328-247) This invention relates to signal modulating devices and more particularly to a device which can modulate a signal in accordance with a decision which has been made after the signal to be modulated is in existence.

Signal modulating devices have found widespread use in industrial controls, in the communications art and in data processing art.

In certain industrial processes it is often necessary to perform an operation or to do work for a regulated, but variable, period of time. By way of example, in certain electrical welding operations it has been found advantageous to regulate the build-up of metal in making a welded joint. This regulation of metal build-up is accomplished by a determination of certain characteristics of the molten metal, after heat has been applied from the welding machine, and a subsequent decision as to how long to apply heat to the metal. The heat control signal in this application must be modulated by a decision which is made after the control signal which causes the heat to be applied, has been initiated.

in certain high speed data processing operations it is sometimes necessary to provide an alarm signal which indicates that a certain condition has been detected, irrespective of whether or not this certain condition has been in fact detected. 'In such operations it is only after the initiation of such an alarm signal that a decision can be made as to whether or not the certain condition exists, and if it does not exist the alarm signal is terminated early. The alarm signal in this example must be modulated in accordance with a decision made after the alarm signal is in existence.

Although the present invention has great utility in applications of the type just described, it can also be employed to great advantage in a pulse modulating arrangement such as those used with communication systems to transmit intelligence. It can be further categorized and used as a voltage controlled phantastron, monostable multivibrator or variable signal delay circuit.

It is an object of the present invention to provide an improved signal modulating device.

It is a further object of the present invention to provide a device which, in response to an applied input signal, will provide an output signal whose length can be varied in accordance with a decision made after the output signal has been initiated.

It is a further object of the present invention to pro vide a signal modulating device which can modulate a signal in response to a predetermined reference signal.

In accordance with a main feature of the present invention there is provided an electron flow control means which has at least two control elements. This electron flow control means is capable of operating in two different states of conduction. When the electron flow control means is conducting in its first state there is provided therefrom a first valued output signal, and when said electron flow control means is conducting in its second state there is provided therefrom a second valued output signal.

In accordance with another main feature of the present invention there is provided input signal circuitry which includes both: (1) an electron storage means having a discharge path and which is connected to a first of the dddZZd i control elements mentioned above, and (2), a feedback circuit coupled to enable the discharge of said electron storage means. The signal input means in response to an applied input signal switches said electron flow control means from its first state of conduction to its second state of conduction and further initiates and provides a linear discharge of the electron storage means. The electron flow control means keeps conducting in its second state until said electron storage device discharges to a predetermined level which results in a reversion of said electron flow control means to said first state of conduction.

in accordance with another main feature there is provided a signal comparison means which compares the discharge signal of thelast-mentioned feature with a reference signal to provide an output signal. The output signal in turn is transmitted to a second one of the control elements of said electron flow control means thereby eifecting a transferral to said first state of conduction before said electron storage device discharges to the predetermined level mentioned above.

The foregoing and other objects and features of this invention will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings wherein FIG. 1 is a schematic diagram of the signal modulating circuit;

FIG. 2 is a graphic diagram showing a discharge signal related to time.

In the description to follow the circuit is described as using two triode tubes and a pentagrid tube. It is to be understood that the circuit will operate with transis tors which are properly connected in a network instead of the combination of the two triodes and pentagrid tube. The pentagrid tube 11 may be a GE 5915 tube manufactred by General Electric Co., or some suitable substitute. in general, the circuit operates to set the pentagrid tube ilinto one of two states of conduction. When only the lower half of the tube 11 conducts (this being the first state of conduction), the screen 13 acts as the plate providin conventional current flow from reference potential 14, via screen 13, to cathode 15. In the first state of conduction the anode 37 is non-conducting (cut-off). Simultaneously there is relatively heavy grid (conventional) current flowing from the reference potential source 16, across the resistor 17, via the grid 19 to cathode 15. Connected to the cathode 15 are two current paths along which current flows while the tube 11 is conducting in the first state, the first being across resistor 21 to the negative reference potential source 23, and the second being through the diode 24 to ground. This first state of conduction is the quiescent condition of the tube 11 and can be considered the standby state of the circuit. In this quiescent condition the point 25 is clamped to ground potential level through diode 2.4. With point 25 clamped to ground in the quiescent condition the output signal at terminal 29 is at ground potential level. As will be explained hereinafter in detail, the pentagrid tube 11 is set, or transferred during the intended operation of the circuit to its second state of conduction. In the second state of conduction conventional current flows from the reference potential source 16 across the resistor 31, through the pentagrid tube 11 to the cathode 15, and simultaneously there is a similar amount of current flowing from the reference potential source 14 via the screen 13 to the cathode 15. The current flow in the second state. of conduction is relatively small, and the point 25 becomes clamped to a 30 volt level through diode 27 to provide the second valued output signal at terminal 29. When the pentagrid tube 11 terminates conduction in its second state (from anode 37 to cathode 3 15), it reverts to its quiescent condition (first state of conduction), and the output signal level returns to ground potential. The two levels of the signal are shown by an illustration of a gate signal 35. The controlled termination of the second state conduction of the pentagrid tube ll provides for a controlled variation or modulation of the length of the output signal.

The circuit in FIG. 1' is shown with certain values assigned to the circuit components. The values are strictly by way of example and might well be other values, provided the entire circuit is designed in accordance wit any particular set of circuit parameters.

Consider now in more detail the switching of the pentagrid tube 11 from its first state of conduction to its second state of conduction, and vice versa. Assume, first that the tube 11 is in its first state of conduction, or quiescent condition. During the first state of conduction point 25 will be held'at ground potential through the clamp circuit consisting of diode 24 connected to ground. As explained before, there will be conventional current flowing from the voltage reference source 14, via screen 13, to cathode 15, and this current will have a value of approximately 2.9 milliamperes. conduction there will be approximately .3 millampere of current flowing across the resistor 17. The point 41 (considering the voltage drop from grid 19 to cathode 15 to be negligible), is also at ground potential and cannot rise above ground potential in this first state of conduction because of the clamp circuit mentioned above. Also, at this standby time the triodes 43 and 45 are both conducting since there is positive grid bias applied thereto. In this standby state the grids 44 and 46, respectively, of the triodes 43. and 25, are each clamped to +150 volts through triode 45 and therefore the plate 47 of condenser 49 is charged to approximately +150 volts. It will be recalled that point 41 is held at approximately ground potential in the quiescent state, therefore there negative voltage at point 59 resulting from this low conduction of triodc 43 aids the discharge of condenser 49. The current flowing across the resistor 17 is directed to condenser 4-) to accommodate the discharge. The resistor 67 in combination with cathode follower 43, the feedback from anode 37, and the voltage amplification from grid Simultaneously in this first state of will be approximately a 150 volt diiference developed across the condenser 49. 7

Keeping in mind the status of the triodes 43 and 45, as well as the condenser 49 during this standby state, consider the application of the negative pulse 51 to terminal 53. The negative pulse 51 is A.-C.-coup1ed through the condenser 55 to the cathode 57 of triode 45. The application of the negative pulse 51 to the cathode 57 causes the triode 45' to conduct more heavily which biases the "grid 44 more negatively than it was in the standby state. As the grid 44 goes more negative the triode 4? tends to conduct less and it follows that point 59 has a sudden drop in potential. The sudden drop in potential at point 59 renders the grid 19 of tube 11 negative with respect to the cathode 15, since the 150 volts developed across the condenser 4-9 is measured from a relatively more negative value of point 55. The grid 19, being negative with respect to the cathode 15, tends to reduce the current flow from the screen 13 to the cathode 15. The reduction in current flow tends to make the point go more negative toward volts, at which value it clamps through diode 27, as described above.

When the cathode 15 clamps at 30-volts, the grid 65 which is connected to a -30 volt reference source 66 causes conduction to. be initiated from anode 37 to cathode 15 of the pentagrid tube 11 and thereafter there is conventional current flowing from the voltage source 16, across resistor 31, to anode 37, across the pentagrid tube 11 to the cathode 15. The current thus flowing in this second state of conduction is in the order of 150 to 330 micro- V 4-1 to anode 37, provide a linear discharge of condenser 49. A constant current flows through resistor 17 which results in holding the point 41 at approximately a constant voltage which is negative relative to cathode 15.

in response the point 59 commences moving more negatively toward l50 volts and consequently grid 44- and the anode 37 also approach -150 volts. Termination of anode current causes the anode 37 to rise rapidly to +300 volts, which in turn causes the triode 43 to conduct more heavily thus raising the voltage level of point 59.

Simultaneously with the activity last mentioned the condenser 49 becomes charged positively with respect to point 55 thereby turning ON the lower half of the tube 11 to provide conventional current flow from the screen 13 to cathode 15. When the lower half conducts, which is the first state of conduction, it in turn causes the terminal 2 to be clamped to ground thereby providing the trailing edge 6: of the gate signal 35. I In the normal operation the point 59 (hence anode 37) is not permitted to drop to 30 volts. Assumetbat the circuit or" F G. l is being used as a pulse modulator in a communication system transmitting intelligence. Further assume that the bit of information to be transmitted could be represented by having the gate signal 35 remain at 30 volts for a period of time that would equal the time t in PEG. 2. it becomes evident from the ramp function graph of the discharge signal, in FIG. 2, that point 59 would be at 100 volts at the end of time t.

Therefore to accomplish providing a signal whose intelligence is represented by the length I at the output terminal 2i, a i'eference voltage of 100 volts is applied to terminal 71. When the voltage at point 59 drops to 100 volts there is an output signal from the voltage coincidence circuit 73 which triggers the negative pulse generator 75. A negative pulse is generated at negative pulse generator 75 which pulse is A.-C.-coupled through the condenser 77 to the grid 65. When the grid 65 goes negative with respect to cathode 15 the current flowing from anode 37 to cathode 21 is cut off and the anode 37 rises rapidly to +300 volts. The remainder of the switching operation is identical with that described above.

It becomes clear from this last-described operation that a decision signal or a predetermined reference signal is applied to ter ninal 71. When point 59, which is following a ramp-type decrease in voltage value reaches the reference signal value, or decision signal value, the grid 65 is biased negatively with respect to the cathode thereby transferring the tube 11 to its first state of conduction. A transfer of tube ill from its second state of conduction to first state of conduction and vice versa, constitutes module ii. g the output signal at terminal 29. Because the point 5% follows a linear decline in voltage, the output signal length can be related to time thereby enabling a voltage decision signal to regulate, for instance, the Work in time that an industrial machine should do.

nile l have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. A voltage-controlled delay phantastron circuit comprising: a cathode coupled phantastron circuit having a cathode follower in its timing capacitor recharge path, an amplitude comparator having a first and a second input terminal and an output terminal, said first and second input terminals connected respectively to an output voltage terminal of the cathode coupled phantastron circuit and a reference voltage source, said comparator output terminal connected to a control electrode of the phantastron multigrid tube to thereby provide a phantastron circuit having a fixed period in its triggered state with a means of prematurely terminating said fixed period under control of a voltage reference level.

2. A voltage-controlled delay phantastron circuit as set forth in claim 1 wherein said output voltage terminal of said cathode coupled phantastron circuit is the output terminal of the cathode follower in the timing capacitor rechar e path and said control electrode of the phantastron multi-grid tube is the third grid of a pentagrid converter.

3. In a cathode coupled phantastron circuit of the type utilizing a cathode follower to speed the recharging of the timing capacitor, a means of prematurely terminating the triggered condition period of said phantastron, said premature termination means comprising: an amplitude comparator having a first and a second input terminal and an output terminal, said first input terminal connected to an output terminal of said phantastron circuit, said second input'terminal connected to a reference voltage source and said output terminal of said comparator connected to a control electrode of the multi-grid tube of said phantastron circuit, thereby enabling said comparator means to terminate, if necessary, the triggered condition of said phantastron circuit prior to its normal duration by control of a reference voltage level.

4. In a cathode coupled phantastron circuit of the type utilizing a cathode follower in the feedback circuit to provide a low resistance recharging path for the timing capacitor and a unilateral current conducting means in the triggering path to the plate of the multi-grid tube of said phantastron circuit, a voltage controlled variable delay circuit comprising an amplitude comparator having two input terminals, one of which connects to the output of the cathode coupled phantastron circuit and the other to a voltage reference source having a predetermined voltage level, said amplitude comparator also having an output terminal connected to the trigger signal input of a triggerable negative pulse source, said negative pulse source connected to a control electrode of the multi-grid tube of said phantastron to provide a negative pulse thereto upon triggerable activation by said amplitude comparator in response to amplitude equality between signals to said comparators input terminals, to thereby control the delay pulse duration corresponding to the triggered condition of said phantastron circuit by terminating said triggered condition prior to the fixed period duration of said phantastron circuit by control of the signal from said voltage reference source to said comparator.

5. The phantastron circuit as set forth in claim 4 Wherein said output terminal of the phantastron circuit is the cathode electrode of the cathode follower in the feedback circuit and said control electrode of the multi-grid tube connected to the negative pulse source is grid number three of a pentagrid converter.

6. The phantastron circuit of claim 5 wherein the cathode electrode of the pentagrid converter is a second output terminal of the phantastron connected to the common junction of the cathode and the plate electrode respectively of a first and a second diode serially connected in the same direction, the plate electrode of said first diode connected to a zero voltage reference level and the cathode electrode of the second diode connected to a negative voltage reference level to provide at the common junction of said diodes a negative going rectangular output pulse having triggered monostable periods corresponding to those of the variable voltage delayed phantastron circuit.

References Eited by the Examiner UNITED STATES PATENTS 2,512,750 6/50 Potter 328-247 2,562,188 7/51 Hance 328-185 2,887,578 5/59 Wolf 328-128 3,002,15 8 9/61 Mitchell et al. 331-152 3,102,240 8/ 63 Cornell 328-247 FOREIGN PATENTS 588,417 5/47 Great Britain.

OTHER REFERENCES Waveforms, vol. 19, MIT Radiation Laboratory Series, McGraW-Hill, 1949, pp. 285-287.

Electron-to-Be Circuits, Seely, McGraw-Hill, 1950, pages 432-434.

ARTHUR GAUSS, Primary Examiner. GEORGE N. WESTBY, Examiner. 

1. A VOLTAGE-CONTROLLED DELAY PHANTASTRON CIRCUIT COMPRISING: A CATHODE COUPLED PHANTASTRON CIRCUIT HAVING A CATHODE FOLLOWER IN ITS TIMING CAPACITOR RECHARGE PATH, A AMPLITUDE COMPARATOR HAVING A FIRST AND A SECOND INPUT TERMINAL AND AN OUTPUT TERMINAL, SAID FIRST AND SECOND INPUT TERMINALS CONNECTED RESPECTIVELY TO AN OUTPUT VOLTAGE TERMINAL OF THE CATHODE COUPLED PHANTASTRON CIRCUIT AND A REFERENCE VOLTAGE SOURCE, SAID COMPARATOR OUTPUT TERMINAL CONNECTED TO A CONTROL ELECTRODE OF THE PHANTASTRON MULTIGRID TUBE TO THEREBY PROVIDE A PHANTASTRON CIRCUIT HAVING A FIXED PORTION IN ITS TRIGGERED STATE WITH A MEANS OF PREMATURELY TERMINATING SAID FIXED PERIOD UNDER CONTROL OF A VOLTAGE REFERENCE LEVEL. 